When you click the Create List button from the Fields View you can enter in a Code (stored value) and a Label/Description (displayed value) but there is no option to define the Split and Merge Policies. You need to use the rest services or the ArcGIS API for Python / alternative API. (Merge Polices for Range Domains)
![Clubdebambos_0-1694767348904.png Clubdebambos_0-1694767348904.png](https://community.esri.com/t5/image/serverpage/image-id/80755iA15AAAD3F47F50E7/image-size/medium?v=v2&px=400)
This option should be made more accessible from the page where you are creating the domains.
![Clubdebambos_1-1694767490517.png Clubdebambos_1-1694767490517.png](https://community.esri.com/t5/image/serverpage/image-id/80756iEEAF0EBB5C60AEBE/image-size/medium?v=v2&px=400)
Same when creating a Range Value Domain, no Split/Merge Policy available.
![Clubdebambos_0-1694770109003.png Clubdebambos_0-1694770109003.png](https://community.esri.com/t5/image/serverpage/image-id/80760iFEE65E1705CC14E3/image-size/medium?v=v2&px=400)